Doctors have expressed "huge concern" that super-gonorrhoea has spread widely across England and to gay men.

The new superbug prompted a national alert last year when it emerged in Leeds, as one of the main treatments had become useless against it.

Public Health England acknowledges measures to contain the outbreak have been of "limited success".

Doctors fear the sexually transmitted infection, which can cause infertility, could soon become untreatable.

Cases of super-gonorrhoea have now been detected in the West Midlands, London and southern England.

Only 34 cases have been officially confirmed in laboratory testing, but this is likely to be the tip of the iceberg of an infection that can be symptomless.

'Infections spread faster'

The outbreak started in straight couples, but is now being seen in gay men too.

"We've been worried it would spread to men who have sex with men," Peter Greenhouse, a consultant in sexual health based in Bristol, told BBC News.

"The problem is [they] tend to spread infections a lot faster simply as they change partners more quickly."

They are also more likely to have gonorrhoea in their throats. There further resistance is more likely to develop as antibiotics get to the throat in lower doses and the area is also teeming with other bacteria that can share the resistance to drugs.

The bacterium that causes gonorrhoea is extremely adept at shrugging off our best antibiotics.

So two drugs - azithromycin and ceftriaxone - are used in combination.

But now resistance to azithromycin is spreading, doctors fear it is only a matter of time before ceftriaxone fails too.

What is gonorrhoea?

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The disease is caused by the bacterium called Neisseria gonorrhoeae.

The infection is spread by unprotected vaginal, oral and anal sex.

Of those infected, about one in 10 heterosexual men and more than three-quarters of women, and gay men, have no easily recognisable symptoms.

But symptoms can include a thick green or yellow discharge from sexual organs, pain when urinating and bleeding between periods.

Untreated infection can lead to infertility, pelvic inflammatory disease and can be passed on to a child during pregnancy.

Safe sex urged

And Dr Gwenda Hughes, the head of the sexually transmitted infections unit at Public Health England, said: "We cannot afford to be complacent.

"If strains of gonorrhoea emerge that are resistant to both azithromycin and ceftriaxone, treatment options would be limited as there is currently no new antibiotic available to treat the infection."

She is encouraging people to practise safe sex to minimise the risk of sexually transmitted infections.

There is also a concerted campaign to find the sexual partners of people who have the superbug.

But a Public Health England report acknowledges this has been of "limited success" so far.

Of 50 sexual partners reported, only 22 were successfully followed up, but, worryingly, 94% of partners tested had the infection.

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The British Association for Sexual Health and HIV said there needed to be a rapid response to the infection and has warned its members to be on the lookout.

Its president, Dr Elizabeth Carlin, said: "The spread of high level azithromycin-resistant gonorrhoea is a huge concern and it is essential that every effort is made to contain further spread.

"Failure to respond appropriately will jeopardise our ability to treat gonorrhoea effectively and will lead to poorer health outcomes for individuals and society as a whole."

But Mr Greenhouse warned that sexual health services were facing their "biggest restriction ever" due to funding cuts.

'Perfect storm'

The emergence of a dangerous superbug was creating a "perfect storm scenario", he said.

Meanwhile, the Department of Health has announced a new tool to help GPs cut the number of antibiotics they prescribe.

It will allow practices to see how their antibiotic prescribing habits compare with other practices.

Health Secretary Jeremy Hunt said: "I want to see antibiotics being prescribed only when necessary and hope this will be a new weapon to help GPs cut the numbers of antibiotics needlessly being given out."